Their point is that that is wishful thinking. If someone violates the law, which does happen, your data can get out. "No longer yours" in this context means "others may disseminate it without your approval". They may be penalized for doing so, but it is absolutely in their power to do so.

You're absolutely right on a legal basis, but people (and companies) act on a spectrum between "legal", "moral", and "what I can get away with".

Sure.

The law also states that crime is illegal.

I wouldn't walk around Compton late at night with a £5K camera though. Even with insurance.

What a law says and what in effect happens is not really the same. How do you GDPR a data breach? How do you DMCA a data breach?